Small errors when baking displacement maps
Looks like a baking bug to me.

Investigation shows the artifacts are already present in the .exr and the displace works as intended. I just subdivided a plane to 16.78M polys for 4096 texture and it showed the same result as you posted.

Artifacts in .exr:



Then I tried converting the curves into mesh, different curves resolutions and smoothings, normalized/unnormalized bakes but I always got black pixels at different random spots.

When I plug the raw bake into compositing nodes and inspect it it has artifacts, so it is not the exr.

The only solution that worked for me are smooth modifiers after the displacement, which is not really a solution.